GaN is a semiconductor with excellent physical properties, such as a large bandgap, a high electric breakdown field, and relatively high electron mobility. Devices fabricated on this semiconductor are especially suitable for use in power electronic applications. Studies show that the Group III-nitride semiconductors of a hetero-structure of AlGaN/GaN are an excellent material system for fabricating high electron mobility transistors (HEMT). The structure supplies an excellent and unique combination of high carrier concentration and high carrier mobility.
There is a requirement to isolate GaN devices for integrated circuit applications. Conventionally, a lateral isolation structure formed by ion-implantation or shallow etching is used to interrupt a highly conductive two-dimensional electron gas (2DEG) layer that forms a channel of HEMT devices. However, this isolation structure is not adequate for multiple devices at different bias conditions (i.e. different voltages applied to the terminals of the devices) due to generation of a back bias effect from a semiconductor substrate. The back bias effect will impact the breakdown voltages and the electrical characteristics of the transistors.
Therefore, development of a semiconductor structure with a simple and appropriate isolation structure and being capable of eliminating the back bias effect is desirable.